MacLennan and Logan Ancient, Weathered and “Modern” (as used on this web site).
Generally speaking, the “Ancient” tartan colours are intended to look similar to those produced by vegetable dyes.
More MacLennan tartan examples from the Kilbarchan Weaver’s Cottage Museum, Renfrewshire (courtesy Geoff Bell):
According to a display at the Fort William West Highlands Museum, the colours of tartans originally depended entirely on what plants grew locally. Fiber or yarn was dyed locally and woven locally – or (maybe) sent off to a weaver to be woven. (A weaver would normally receive a bucket of thread, already died and ready for weaving – and the pattern to be woven.) Most families would have woven their own fabric until 1800, or even 1850. Initially, patterns were simply different regional checked-cloth patterns, chosen by the weaver’s preference – in the same way as people today choose what colours and patterns they like in their clothing. Clans often identified themselves more by a sprig of plant than with a tartan pattern. Sprigs (not patterns) identified clans as late as 1745. Patterns did not become ‘fixed’ until the Victorians and chemical dyes. Prince Albert designed many tartan patterns.
‘Kilts & Tartan Made Easy‘ by Scottish Tartan Authority Governor Dr Nicholas J Fiddes is a simple, free guide to wearing kilts. More about colours. The wearing of tartans was prohibited by an Act of parliament in 1746/47: More about tartan prohibition.